Integrated circuit (IC) technologies are constantly being improved. Such improvements frequently involve scaling down device geometries to achieve lower fabrication costs, higher device integration density, higher speeds, and better performance.
Lithography is a mechanism by which a pattern on a mask is projected onto a material layer. As feature sizes decrease, immersion lithography, in which the exposure procedure is performed with a liquid filling the space between the material layer and lens, is often used. Using immersion lithography allows for higher numerical apertures (NA) than when using lenses in air, and therefore, provides for improved resolution. Furthermore, immersion lithography provides enhanced depth-of-focus (DOF) for printing smaller features.